Deer at 1000yds , all thats needed is a 260 Remington , I killed just short of 1K this year no problems. In a mauser action I'd go with a 6.5-06 to get an extra 200fps out of it.

Now 1500yds is a whole nother story that added 500yds is a LOOOONG way past 1000yd , I'd say a 180gr Berger launched at say 3000fps , maybe froma 7mmRUM or close , a 240gr Sierra Match King launched at 2900-3100 fps , for a 300RUM minimum more like a 30-338 Lapua imp of 300AX , or maybe the biger 338's ike the Edge or 338 Lapua imp or 338-378Wby , andhting to get a realy high BC bullet .680+ out close to 2800+fps so do on a deer at 1500yds

Better be an excellent shot who knows exactly what he is doing rather than someone who wants to sling lead "spray and play" so to speak. A deer sized animal at that range using the 260 for example will require precise shot placement and that involves virtually perfect wind reading ability to place the shot in the vital zone(not to mention the rifle and ammunition capable of doing it). Just remember at 1k with the 260 you are almost without exception well below 500 ft-lb’s of energy and using most bullets with just a 7mph 90 degree to POA your drift will vary between 4.5 and 6 feet.

Long rang shooting requires proper equipment, experience and skill not necessarily in that order..

For 1500yds BC and bullet weight become extremely important. Guys seem to be having sucess with the 338 calibers at long range. Speed is important too so I'd go with 338 Edge, 338 Lapua among others with pleanty of room for powder. The 300gr Sierra Match King is excellent having a BC of .768. A heavy bullet insures pleanty of energy at long range.